Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$49.89	9.353%	$54.5562	$54.56	$54.55	$54.60
Purchase #2	$81.42	13.212%	$92.1772	$92.18	$92.20	$92.20
Purchase #3	$87.89	6.191%	$93.3313	$93.33	$93.35	$93.30
Purchase #4	$84.65	4.321%	$88.3077	$88.31	$88.30	$88.30
Purchase #5	$50.91	5.572%	$53.7467	$53.75	$53.75	$53.70
Purchase #6	$74.27	6.112%	$78.8094	$78.81	$78.80	$78.80
Purchase #7	$136.73	10.154%	$150.6136	$150.61	$150.60	$150.60
7 purchase totals =	$565.76		$611.5421	$611.55	$611.55	$611.50